Spectral analysis of Ahuna Mons from Dawn mission's visible‐infrared spectrometer

Abstract

Ahuna Mons is the highest mountain on Ceres. A unique complex in terms of size, shape, and morphology, Ahuna is bordered by flanks of the talus around its summit. Recent work by Ruesch et al. () based on Dawn's Framing Camera images shed light on the possible origin of Ahuna Mons. According to Ruesch et al. (2016), Ahuna Mons is formed by a volcanic process involving the ascent of cryomagma and extrusion onto the surface followed by dome development and subsequent spreading. Here we analyzed in detail the composition of Ahuna Mons, using data acquired by the visible and infrared spectrometer aboard Dawn. The spectral analysis reveals a relatively high abundance of carbonates and a nonhomogeneous variation in carbonate composition and abundance along Ahuna's flanks, associated with a lower amount of the Ceres's ubiquitous NH4‐phyllosilicates over a large portion of the flanks. The grain size is coarser on the flanks than in the surrounding regions, suggesting the presence of fresher material, also compatible with a larger abundance of carbonates. Thermal variations are seen in Ahuna, supporting the evidence of different compactness of the surface regolith in specific locations. Results of the spectral analysis are consistent with a possible cryovolcanic origin which exposed fresher material that slid down on the flanks.

Constraints on Ceres' Internal Structure and Evolution From Its Shape and Gravity Measured by the Dawn Spacecraft

“…The simplest explanation is that Ceres' crust is neither purely ice (the case studied in Bland, ) nor purely rock but an ice‐rock‐salt hydrate mixture that allows some relaxation at the longest wavelengths but is able to support the topography on the shorter wavelengths over geologic timescales. This suggested composition is supported by visible and infrared spectrometer (VIR) observations, which detected salts in the form of sodium carbonates and ammonium salts at Occator (De Sanctis et al, ), as well as sodium carbonates at Ahuna Mons (Zambon et al, ). Adding silicates or salts into water ice increases crustal density, implying that the crustal density must exceed a minimum value in order to meet the required mechanical strength.…”

Mineralogy and temperature of crater Haulani on Ceres

“…; Zambon et al. ), such as Cerealia Facula in the middle of crater Occator, or enriched in organics similar to those discovered in the region of crater Ernutet (De Sanctis et al. ; Pieters et al.…”

“…The northern flanks of Ahuna Mons, the highest mountain on Ceres, also display a larger amount of Ca‐carbonates and Na‐carbonates compared to surrounding regions (Zambon et al. ). Water‐ice–rich units mixed with low‐albedo components were discovered only in about 10 specific places at the surface, at latitudes poleward of 30° in fresh craters near rim shadows (Combe et al.…”

Geological mapping of the Ac-10 Rongo Quadrangle of Ceres

“…The steep ( ∼30-40 °) flanks of Ahuna Mons are composed of a bright (high albedo) material that has been proposed to consist of salts . Recently, Zambon et al (2017) concluded that the edifice exhibits high abundances of carbonates and low portions of hydrous minerals relative to the average surface composition of Ceres. The appearance and composition of Ahuna Mons make it Ceres' most unique landform and, along with Occator's bright spots, among the most interesting of Dawn's discoveries.…”